Although a wide variety of coatings is available for coating or painting metal surfaces of subjects, an ideal coating system—one with all the desired performance properties, simple application, and low cost—is difficult to find. Many factors such as the purpose of coating, costs, government regulations, service environment, subject [also called substrate] and service conditions, basic functions, and application limitations must be considered.
Corrosions of metals, such as steel and iron, occur in all environments. Needs are different for different metal, different substrate [subject], different service environment, and the different period required for having protection. In addition, one must consider properties like resistance to heat, cold, sunlight, weathering and other conditions during the time the protection is needed.
In addition to all of these requirements, low VOC and/or low HAP paints or coatings using water as a carrier instead of petroleum-based solvents are becoming more desirable as both the society, the users and the manufacturer look for ways to reduce and minimize impacts on the environment when such coatings or paints are used. The levels of emissions from aqueous coating systems are lower than those from solvent-borne surface coatings.
Coatings are routinely applied to metal surfaces or surfaces of metal subjects to provide various protections. Many metal subjects may only need short-term protection against corrosion or rusting when these subjects are being delivered, stored on site, and being assembled or erected. This particularly true for steel subjects like open web and long span steel joists and joist girders, structural steel, cold formed steel framing and others.
It is therefore desirable to have a water based coating material with low VOC and essentially HAP free and at the same time the aqueous coating can be conveniently applied to structural metal parts such as steel joist by dipping, flow painting, spraying and other similar methods.